Hi Marijn,<div><br></div><div>FrTime propagates changes asynchronously. When send-event returns, there&#39;s no guarantee that the event has finished propagating through the system. And in general, (value-now b) is not well-defined, since asynchronous processing makes it difficult to define what &quot;now&quot; means; programs should only call this if they can tolerate stale values.</div>

<div><br></div><div>(It so happens that evaluating (hold a) blocks your thread until the event finishes propagating, but that&#39;s an implementation detail. You can probably achieve the same effect through a call to &quot;sleep&quot;, for example.)</div>